Download Chapter 18 Notes

Chapter 18 Notes
18.1 – Structure of the Atom
-Scientists use short hand or an element name by either writing it with one capital letter
or one capital and one lower case letter.
Ex- C or Al
- Scientists get elements names and symbols from the original Latin manes of the
element, names of the scientists, names of the places or properties of the element.
An element is made up of ATOMS- Smallest piece of matter that still retains the property
of the element.
Atoms have 3 parts:
Proton- Positively charged
Neutron- No Charge
Electron- Negatively charged
*Protons and Neutrons are in the nucleus together. (Most mass in the atom)
Electrons float around the nucleus in an electron cloud. (Most space in the atom)
Protons and Neutrons are made up of QUARKS- 3 Quarks make up a proton & 3 make
up a neutron. (6 quarks total)
-Discovered by smashing charged particles into a proton and breaking the protons
apart.
**Know the 5 atomic models on Pg 548 and know the names
1. Dalton’s Atom- Solid sphere
2. Thompson’s Atom- positive main mass with electrons attached to the outside of it.
3. Rutherford’s Atom- Positive nucleus in center with electrons orbiting around nucleus
like planets.
4. Bohr’s Atom- Protons and neutrons in the nucleus, with electrons orbit around nucleus
like planets.
5. Electron Cloud Model- Protons and neutrons in the nucleus with electron in energy
levels around it.
- Pneumonic- Don’t Take Rabbits Bed Eeyore!
- Changes in the model occurred due to experiments and learning about new parts
of the atom.
- Current model of the atom is the electron cloud model- where electrons travel at
an average distance from the nucleus depending on the electron’s energy –Energy
levels.
18.2 – Masses of atoms
- Protons and neutron are basically the same size.
-Electrons are about 2000 times smaller, so it’s mass isn’t used when finding the mass of
an atom.
- Atomic Mass- The total # of protons and Neutrons
-Atomic Number- # of protons
*The # of electrons ALWAYS equals the # of protons in an atom.
*To find # of Neutrons, you subtract the atomic # from the atomic mass
(after it’s a whole number)
Nuclear Symbol- a way to represent the symbol, mass, and atomic # of an element
Element
Symbol
X
Atomic Mass
Ex: Pb 207
82
Atomic #
*Scientists also use a Name/symbol-mass shortcut
Carbon- 12 atomic mass (rounded)
Or C-12
Isotopes- Atoms of the same element that has a different number of neutrons, but same
number of protons.
- Normal element of carbon is Carbon-12 (Mass),
*so the Atomic Number is 6 and therefore it has 6 protons, & 6 neutrons.
-Isotope of carbon- Carbon-14
*Atomic # is still 6, so you have 6 protons & 8 Neutrons.
*They use how much each isotope occurs and it’s mass to determine the Average
atomic mass.
Ex- IF you have an average atomic mass of 35.95 and 4 isotopes X-33, X-34, X-35 and
X-36 which would occur most often? (X-36 because Average atomic mass is so close to
it)
18.3 – The Periodic Table
-Dmitri Mendeleev created our 1st periodic table, by organizing the elements by
increasing masses, but left spaces for elements that hadn’t been discovered yet, that
eventually fit into his spaces.
-Joseph Moseley created our current periodic table by organizing the element by atomic
number.
HOW THE PERIODIC TABLE IS ORGANIZED:
- Groups- (also known as FAMILIES)
-Vertical columns in the periodic table labeled as 1- 18 or I A – VIII A
*Groups have similar properties, which get stronger as you move down
the column. (all alkali metals react violently with water)
*The closer the elements are in the column the more they have in common
with each other.
*Groups always have the same number of electrons in the outer energy
level. (Except He) This is known as VALENCE ELECTRONS
-Ex- group 1 or IA has 1 electron in the energy levels.
-Electrons have different amount of energy, and therefore are
placed in different energy levels. You ALWAYS have to fill a
lower level before you start to fill the next level.
Energy Level Diagram
2nd Energy LevelHolds up to 8
Electrons
3rd Energy Level- Holds
up to 8 Electrons
Nucleus
1st Energy LevelHolds up to 2 electrons
Periods- Horizontal rows that increase in the number of electrons and end when the outer
energy level is full of electrons
-# Tells you how many energy levels you have in an energy level Diagram.
*Ex- Lithium has 3 electrons, so 2 electrons fill the 1st energy level, and 1
electron fill the 2nd energy level. (Lithium is in period 2= 2 energy levels)
Electron Dot Diagram- Uses the symbol of the element and dots to represent the outer
level electrons.
O
-Oxygen has 8 electrons total, so 2 fill the first level, 6 fill the 2nd level, and
therefore you have 6 on your outer most level. So you write the symbol of
oxygen and put 6 dots around it, with no more than 2 dots per side of the symbol.
Metals- Metalloids- Non-Metals:
Metals- Found on the left hand side of the stair step on the periodic table, usually in the
solid form, (except mercury), are lustrous (shiny), ductile (drawn into wires), malleable
(Pounded into sheets), and are good conductors of heat and electricity.
Non-Metals- Found on the right hand side of the stair step on the periodic table, usually
in the gas state. they are brittle and poor conductors of electricity.
Metalloids- Found on the stair step (except for aluminum which is a metal) They contain
properties of both metals and metalloids.
-Only the elements on the STRAIGHT SIDES of the stair step are metalloids!